Introduce the new print_strings flag in btf_dump_type_data_opts. If
enabled, libbpf will print character arrays as strings if they meet the
following conditions:
- Contains a nul-termination character ('\0')
- Contains only printable characters before the nul-termination character
If print_strings is set to false (default value), the existing
behavior remains unchanged.
With print_strings=false:
str_array = (__u8[14])[
'H',
'e',
'l',
'l',
'o',
],
With print_strings=true:
str_array = (__u8[14])"Hello",
Signed-off-by: Quentin Deslandes <[email protected]>
---
tools/lib/bpf/btf.h | 3 ++-
tools/lib/bpf/btf_dump.c | 25 ++++++++++++++++++++++++-
2 files changed, 26 insertions(+), 2 deletions(-)
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 8e6880d91c84..cf190900d483 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -284,9 +284,10 @@ struct btf_dump_type_data_opts {
bool compact; /* no newlines/indentation */
bool skip_names; /* skip member/type names */
bool emit_zeroes; /* show 0-valued fields */
+ bool print_strings; /* print char arrays as string */
size_t :0;
};
-#define btf_dump_type_data_opts__last_field emit_zeroes
+#define btf_dump_type_data_opts__last_field print_strings
LIBBPF_API int
btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c
index 4d9f30bf7f01..d396a10f37b2 100644
--- a/tools/lib/bpf/btf_dump.c
+++ b/tools/lib/bpf/btf_dump.c
@@ -67,6 +67,7 @@ struct btf_dump_data {
bool compact;
bool skip_names;
bool emit_zeroes;
+ bool print_strings;
__u8 indent_lvl; /* base indent level */
char indent_str[BTF_DATA_INDENT_STR_LEN];
/* below are used during iteration */
@@ -2021,6 +2022,21 @@ static int btf_dump_var_data(struct btf_dump *d,
return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0);
}
+static bool btf_dump_isprint_str(const char *data, unsigned int len)
+{
+ unsigned int i;
+
+ for (i = 0; i < len; ++i) {
+ if (data[i] == '\0')
+ return true;
+
+ if (!isprint(data[i]))
+ return false;
+ }
+
+ return false;
+}
+
static int btf_dump_array_data(struct btf_dump *d,
const struct btf_type *t,
__u32 id,
@@ -2047,8 +2063,14 @@ static int btf_dump_array_data(struct btf_dump *d,
* char arrays, so if size is 1 and element is
* printable as a char, we'll do that.
*/
- if (elem_size == 1)
+ if (elem_size == 1) {
d->typed_dump->is_array_char = true;
+ if (d->typed_dump->print_strings &&
+ btf_dump_isprint_str(data, array->nelems)) {
+ btf_dump_type_values(d, "\"%s\"", data);
+ return 0;
+ }
+ }
}
/* note that we increment depth before calling btf_dump_print() below;
@@ -2533,6 +2555,7 @@ int btf_dump__dump_type_data(struct btf_dump *d, __u32 id,
d->typed_dump->compact = OPTS_GET(opts, compact, false);
d->typed_dump->skip_names = OPTS_GET(opts, skip_names, false);
d->typed_dump->emit_zeroes = OPTS_GET(opts, emit_zeroes, false);
+ d->typed_dump->print_strings = OPTS_GET(opts, print_strings, false);
ret = btf_dump_dump_type_data(d, NULL, t, id, data, 0, 0);
--
2.44.0
On Sat, 2024-04-13 at 23:39 +0200, Quentin Deslandes wrote:
> Introduce the new print_strings flag in btf_dump_type_data_opts. If
> enabled, libbpf will print character arrays as strings if they meet the
> following conditions:
> - Contains a nul-termination character ('\0')
> - Contains only printable characters before the nul-termination character
>
> If print_strings is set to false (default value), the existing
> behavior remains unchanged.
>
> With print_strings=false:
> .str_array = (__u8[14])[
> 'H',
> 'e',
> 'l',
> 'l',
> 'o',
> ],
>
> With print_strings=true:
> .str_array = (__u8[14])"Hello",
>
> Signed-off-by: Quentin Deslandes <[email protected]>
> ---
Hi Quentin,
Thank you for this patch, sorry for the delay reviewing it.
Could you please also add a few tests in
tools/testing/selftests/bpf/prog_tests/btf_dump.c ?
[...]
> @@ -2021,6 +2022,21 @@ static int btf_dump_var_data(struct btf_dump *d,
> return btf_dump_dump_type_data(d, NULL, t, type_id, data, 0, 0);
> }
>
> +static bool btf_dump_isprint_str(const char *data, unsigned int len)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < len; ++i) {
> + if (data[i] == '\0')
> + return true;
> +
> + if (!isprint(data[i]))
> + return false;
Would it make sense to use isprint_l() and specify something like C locale?
> + }
> +
> + return false;
> +}
> +
> static int btf_dump_array_data(struct btf_dump *d,
> const struct btf_type *t,
> __u32 id,
> @@ -2047,8 +2063,14 @@ static int btf_dump_array_data(struct btf_dump *d,
> * char arrays, so if size is 1 and element is
> * printable as a char, we'll do that.
> */
> - if (elem_size == 1)
> + if (elem_size == 1) {
> d->typed_dump->is_array_char = true;
> + if (d->typed_dump->print_strings &&
> + btf_dump_isprint_str(data, array->nelems)) {
> + btf_dump_type_values(d, "\"%s\"", data);
Note: this would have to deal with escape sequences,
otherwise strings containing '\' would be printed incorrectly.
> + return 0;
> + }
> + }
> }
>
> /* note that we increment depth before calling btf_dump_print() below;
[...]